The present invention relates to an optical connector assembling adhesive injection pipe (hereinafter referred to as an adhesive injection pipe) for injecting an adhesive, which is used for adhesion of an optical fiber cable, into a ferrule in a connector when the optical fiber connector is assembled.
Normally, an optical fiber cable is comprised of a bare fiber portion made of thin quartz glass or the like with a diameter of 125 .mu.m and a buffered fiber portion coated with a covering layer of nylon or the like on its circumference and having a diameter of about 1 mm.
When the optical fiber cable is attached to an optical connector, if stress or bending force due to compression or the like is locally applied to the optical fiber connector and the optical fiber cable, optical signals transmitting therethrough receives bad influence to cause transmission losses such as outer leakage or loss increase, and finally the optical fiber cable may be disconnected.
Conventionally, when an optical fiber is fixed to a cylindrical ferrule which is a component for constituting an optical fiber connector and has a through hole at the center, a method of using an adhesive is common, and the optical fiber connector has been constructed as follows.
FIG. 5 is a sectional view showing sequential steps of a conventional method of assembling an optical fiber connector. In the method of assembling an optical fiber shown in FIG. 5, a needle 2 is directly inserted into a rear portion of a ferrule 1. In FIG. 5A, the needle 2 is inserted into the rear portion 1A of the ferrule 1 which is a cylindrical member through which an optical fiber passes, and an adhesive 3 is injected. Next, a buffered fiber 4 with an optical fiber 4F exposed at a front end is inserted from a tail portion of the ferrule 1, and the buffered fiber 4 and the optical fiber 4F are adhered to the ferrule 1 (FIG. 5B).
This prior art has problems that an amount of adhesive must be adjusted while observing the tail portion of the ferrule 1 so that the adhesive does not overflow from the tail portion of the ferrule 1 positioned at a deeper portion in a connector housing 5, and further, since the rear portion 1A of the ferrule 1 is at a deeper portion in the housing of the optical connector, even if the adhesive overflows, a wiping operation can not be carried out. If the overflown adhesive flows into the portion between the rear portion 1A of the ferrule 1 and the housing 5 or the portion where a coil spring 6 is mounted as shown in FIG. 5B, there is caused a problem that the ferrule 1 adheres to the housing 5 so that the ferrule 1 can not move in an axial direction.
Japanese Utility Model Registration No. 3019449 discloses a structure that in order to prevent an epoxy resin from entering into parts movable relatively to one another in an optical fiber connector, a tube is inserted into an optical fiber cable insertion path, the front end thereof is fitted in a recess at the rear end of a ferrule, positioning is carried out to prevent the tube from moving in the insertion path, and then an adhesive is injected from the rear end of the tube.
According to this structure, the injection of the adhesive into the optical fiber cable insertion path of the ferrule is made easy by using the tube. However, this structure has a problem that when the optical fiber cable is inserted into a portion from which the tube was removed after the injection of the adhesive, if the amount of the injected adhesive is too large, a surplus adhesive overflow from the insertion path, so that after all, the adhesive enters into the parts movable relatively to one another in the connector. On the other hand, if the amount of the injected adhesive is made small in order to prevent the adhesive from overflowing, another problem occurs such that there is a tendency to lower the fixing strength of the optical fiber cable is caused. Since the portion into which the adhesive is injected is such a portion that an operator can not observe, it is difficult to inject a suitable amount of adhesive.
An object of the present invention is therefore to provide an adhesive injection pipe by which anyone can easily inject a suitable amount of adhesive for adhesion of an optical fiber cable into a connector for an optical fiber cable. Another object of the present invention is to provide a method of assembling an optical connector using the adhesive injection pipe.